Electrochemical conversion cells, commonly referred to as fuel cells, produce electrical energy by processing reactants, for example, through the oxidation and reduction of hydrogen and oxygen. In some fuel cell systems, hydrogen or a hydrogen-rich gas is supplied as a reactant through a flowpath to the anode side of a fuel cell, while oxygen (such as in the form of atmospheric oxygen) is supplied as a reactant through a separate flowpath to the cathode side of the fuel cell. The anode and cathode facilitate the electrochemical conversion of the reactants into electrons and positively charged ions (for the hydrogen) and negatively charged ions (for the oxygen). An electrolyte layer separates the anode from the cathode to allow for selective passage of ions from the anode to the cathode, while simultaneously prohibiting the passage of the generated electrons. The generated electrons are instead forced to flow through an external electrically conductive circuit (such as, a load) to perform useful work before recombining with the charged ions at the cathode. The combination of the positively and negatively charged ions at the cathode results in the production of non-polluting water as a byproduct of the reaction.
A polymer electrolyte fuel cell may comprise a polymer membrane (e.g., a proton exchange membrane (PEM)) with catalyst electrode layers on both sides. The catalyst coated PEM may be positioned between a pair of gas diffusion media (GDM), and placed outside of the gas diffusion media layers are cathode and anode plates. During manufacturing of a membrane electrode assembly, catalyst electrode layers can be coated successively on each side of a membrane support. That is, the layers are formed using sequential coating operations, including partial or complete drying of one layer before the next layer is applied to the membrane support.
Alternatively, catalyst coated diffusion media layers can be used in which the catalyst is coated on gas diffusion media. During manufacturing of catalyst-coated diffusion media, a catalyst electrode layer and an ionomer layer can be coated successively on one side of a substrate. Similar to the manufacturing of a polymer electrolyte fuel cell, the layers are formed using sequential coating operations, including partial or complete drying of each layer before the next layer is applied to the membrane support.
The manufacturing processes are complex, time-consuming, and costly. Where numerous layers are involved, there may be considerable duplication of coating and drying equipment. In some instances, where layers are coated without drying steps between each coating layer, intermixing of the layers and/or the critical ingredients dispersed or dissolved therein can occur. In addition, non-uniform layers having variable layer thicknesses can result.
Therefore, alternative fuel cells, membrane electrode assemblies, and methods for fabricating membrane electrode assemblies are disclosed herein.